The Small Animal Imaging Core is supported primarily through the NCI Small Animal Imaging Resource Program (SAIRP) of which Washington University is one of five centers. NCI SAIRP funding was initiated in September 1999 and will continue for five years providing $3.2 million in total support. Located in the heart of the University's medical complex, the Washington University SAIRP Center provides intellectual and physical resources devoted to magnetic resonance imaging (MRI) and positron emission tomography (PET) directed toward small laboratory animals such as hamsters, rats, mice, etc. The MRI resources include two state-of-the-art 4.7 tesla multi-nuclear scanners with magnet clear bores of 33 and 40 cm. The scanners are driven via Varian UNITY-INOVA consoles and Oxford/Magnex high-performance low-noise gradient systems. The PET resource is centered on a newly designed microPET scanner from Concord Microsystems providing 1.5 mm resolution and high signal- sensitivity Two cyclotrons and an associated radiochemistry laboratory are connected to the PET facility via pneumatic tube system and small bore gas line for transport of liquid (contained in syringes) ang gaseous radio-pharmaceuticals. Both MRI and PET scanners offer sensitivity and resolution optimized for small animal research. Additional resources include facilities for support of small animal imaging including housing, physiologic support and monitoring equipment, surgical procedure rooms, wet-chemistry laboratories and data analysis and archival systems. This Core will make available to members of the Siteman Cancer Center (SCC) the latest in small animal MRI and PET capabilities. Highly skilled staff members are available to assist, advise and collaborate on projects of interest to SCC members.